Stationary fuel cell system

Abstract

To reduce noise of a stationary fuel-cell system with a simple structure.SOLUTION: A control part has a map which shows a correspondence relationship between a control volume Cnt of an auxiliary machine and a noise level of the stationary fuel-cell system 1, a correspondence relationship between generated power Pow of a fuel cell FC and a noise level, or a correspondence relationship between temperature T detected by a temperature detection part St and the noise level, with reference to the map, sets as an upper limit value control volume Cnt corresponding to the noise level equivalent to an allowable value Nth, the generated power Pow corresponding to the noise level equivalent to the allowable value Nth, or temperature T corresponding to the noise level equivalent to the allowable value when trying to keep the noise level of the stationary fuel-cell system 1 at the allowable value Nth or less, and raises target temperature of cooling water or the fuel cell FC when the control volume Cnt of the auxiliary machine, the generated power Pow of the fuel cell or temperature T detected by the temperature detection part St is over the upper limit value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a stationary fuel cell system.

Background Art

[0002] As a fuel cell system, in order to suppress noise of a fan that lowers the temperature of cooling water for cooling a fuel cell, there is a system that suppresses an increase in the rotation speed of the fan by lowering a target temperature of the cooling water in advance when the temperature of the cooling water is estimated to rise. Patent Document 1 is available as a related technology.

[0003] By the way, when a fuel cell system is configured as a stationary fuel cell system installed at a fixed location, noise regulations (allowable noise level values) for the stationary fuel cell system differ under various conditions such as the installation location of the stationary fuel cell system and the time of day, depending on ordinances and rules established by national and local governments. For example, when the system is installed in a residential area, the allowable noise level is lower than when it is installed in an industrial area. Further, when the time zone is midnight, the allowable noise level is lower than that during the daytime.

[0004] Therefore, when the above fuel cell system is configured as a stationary fuel cell system, it is necessary to prepare a plurality of target cooling water temperatures and switch the plurality of target temperatures according to various conditions in order to comply with noise regulations for various conditions such as installation location and time zone, which may complicate power generation control of the fuel cell for noise reduction.

Prior Art Literature

Patent Literature

[0005]

Patent Literature 1

Summary of the Invention

Problem to be Solved by the Invention

[0006] One aspect of the present invention is to provide a stationary fuel cell system that can reduce noise with a simple configuration. [Means for solving the problem]

[0007] One embodiment of the present invention is a stationary fuel cell system comprising a fuel cell, a temperature detection unit for detecting the temperature of cooling water that cools the fuel cell or the temperature of the fuel cell, an auxiliary unit for generating electricity from the fuel cell, and a control unit for controlling the operation of the auxiliary unit so that the temperature detected by the temperature detection unit follows a target temperature.

[0008] The control unit has a map showing the correspondence between the control amount of the auxiliary equipment and the noise level of the stationary fuel cell system, the correspondence between the power generated by the fuel cell and the noise level of the stationary fuel cell system, or the correspondence between the temperature detected by the temperature detection unit and the noise level of the stationary fuel cell system. When attempting to keep the noise level of the stationary fuel cell system below an acceptable value, the control unit refers to the map and sets the control amount corresponding to the noise level corresponding to the acceptable value, the power generated corresponding to the noise level corresponding to the acceptable value, or the temperature corresponding to the noise level corresponding to the acceptable value as an upper limit. If the control amount of the auxiliary equipment, the power generated by the fuel cell, or the temperature detected by the temperature detection unit exceeds the upper limit, the control unit raises the target temperature.

[0009] This allows the fuel cell's power generation to be increased by raising the target temperature when the control amount of the auxiliary equipment, the power generated by the fuel cell, or the temperature detected by the temperature detection unit exceeds the upper limit and the noise level of the stationary fuel cell system is about to exceed the permissible limit. As a result, the rotation speed of the fan that lowers the temperature of the cooling water and the motor in the cooling water pump that circulates the cooling water can be reduced, thereby reducing the noise of the stationary fuel cell system. Furthermore, by referring to maps that show the correspondence between the control amount of the auxiliary equipment and the noise level of the stationary fuel cell system, the correspondence between the power generated by the fuel cell and the noise level of the stationary fuel cell system, or the correspondence between the temperature detected by the temperature detection unit and the noise level of the stationary fuel cell system, an upper limit can be uniquely set relative to the permissible value. Therefore, there is no need to prepare multiple upper limits for various conditions such as the installation location and time of day of the stationary fuel cell system and switch between these multiple upper limits according to various conditions, and the noise of the stationary fuel cell system can be reduced with a simple configuration.

[0010] Furthermore, the control unit may be configured to change the tolerance value based on user instructions.

[0011] This allows the noise level of stationary fuel cell systems to be reduced to the level desired by the user.

[0012] Furthermore, the control unit may be configured to change the allowable value based on instructions transmitted from an external terminal located outside the stationary fuel cell system.

[0013] This makes it possible to reduce the noise level of stationary fuel cell systems to a level transmitted from an external terminal without having to travel to the stationary fuel cell systems installed in remote locations.

[0014] Furthermore, the control unit may be configured to limit the power generated by the fuel cell if, after raising the target temperature, the temperature detected by the temperature detection unit exceeds the target temperature after the rise.

[0015] This can suppress heat generation of the fuel cell FC, thereby suppressing a temperature rise of the fuel cell. In addition, since the control amounts of each auxiliary device, such as the rotation speed of a fan and the rotation speed of a motor in an air compressor, can each be reduced, noise from each auxiliary device can be suppressed.

[0016] Further, the control unit may be configured to, after increasing the target temperature, decrease the target temperature if the impedance of the fuel cell exceeds a threshold value.

[0017] As a result, the target generated power of the fuel cell decreases, so the rotation speed of the motor in the air compressor decreases, the supply amount of oxidant gas from the air compressor to the fuel cell decreases, drying inside the fuel cell is alleviated, and a voltage drop of the fuel cell can be suppressed. Effects of the Invention

[0018] According to the present invention, noise can be reduced with a simple configuration in a stationary fuel cell system. Brief Description of the Drawings

[0019] [Figure 1] It is a diagram showing an example of the stationary fuel cell system according to an embodiment. [Figure 2] It is a diagram showing an example of a map stored in a storage unit. [Figure 3] It is a flowchart showing the operation of the control unit during the silent operation mode in Example 1. [Figure 4] It is a flowchart showing the operation of the control unit during the silent operation mode in Example 2. [Figure 5] It is a flowchart showing the operation of the control unit during the silent operation mode in Example 3. Mode for Carrying Out the Invention

[0020] Embodiments will be described in detail below with reference to the drawings.

[0021] Fig. 1 is a diagram showing an example of the stationary fuel cell system according to the embodiment.

[0022] The stationary fuel cell system 1 shown in Fig. 1 is installed at a fixed location, such as an industrial stationary generator, a domestic stationary generator, or an emergency stationary generator, and is configured to supply constant electric power to a load Lo.

[0023] Further, the stationary fuel cell system 1 includes a fuel cell FC, a fuel tank HT, a main stop valve SV, an injector INJ, a gas-liquid separator GLS, a circulation pump HP, an exhaust and drain valve EDV, a diluter DIL, an air compressor ACP, an air pressure regulating valve ARV, and an air shut-off valve ASV.

[0024] Further, the stationary fuel cell system 1 includes a radiator R, a fan F, a cooling water pump WP, an intercooler IC, a temperature detection unit St, a power converter CNV, a power storage device B, a current sensor Sif, a voltage sensor Svf, a user interface UI, a storage unit 2, a communication device 3, and a control unit 4.

[0025] The fuel cell FC is a fuel cell stack configured by stacking a plurality of fuel cells, and generates electricity by an electrochemical reaction between hydrogen contained in a fuel gas (such as hydrogen gas) and oxygen contained in an oxidant gas (such as air). Note that when the amount of oxidant gas supplied to the fuel cell FC becomes relatively large, the inside of the fuel cell FC (the fuel cells) tends to dry easily. When the inside of the fuel cell FC dries, the fuel cell FC (the electrolyte membrane in the fuel cells) may deteriorate, which may cause a decrease in the voltage of the fuel cell FC.

[0026] The fuel tank HT is a storage container for fuel gas. The fuel gas stored in the fuel tank HT is supplied to the fuel cell FC via the main stop valve SV and the injector INJ.

[0027] The main shut-off valve SV is composed of a solenoid valve and other components, and supplies fuel gas to the injector INJ. The main shut-off valve SV also shuts off the supply of fuel gas to the injector INJ through the operation control of the control unit 4.

[0028] The injector (INJ) adjusts the flow rate of fuel gas so that the pressure of the fuel gas supplied to the fuel cell (FC) remains constant.

[0029] The gas-liquid separator (GLS) separates the fuel gas and liquid water discharged from the fuel cell (FC).

[0030] The circulation pump HP resupplies the fuel gas separated by the gas-liquid separator GLS back to the fuel cell FC.

[0031] The exhaust drain valve (EDV) sends the liquid water separated by the gas-liquid separator (GLS) to the diluent (DIL). The liquid water sent to the diluent (DIL) is stored in a tank within the diluent (DIL). In addition, the fuel gas and oxidizer gas discharged from the fuel cell (FC) merge in the diluent (DIL) and are discharged to the outside of the stationary fuel cell system (1).

[0032] The air compressor ACP compresses the oxidizer gas present around the stationary fuel cell system 1 and supplies it to the fuel cell FC via the intercooler IC and air shut-off valve ASV. The compression ratio of the air compressor ACP is controlled by adjusting the opening degree of the air pressure regulating valve ARV located downstream of the fuel cell FC.

[0033] The intercooler IC exchanges heat between the oxidizer gas, which has become hot due to compression, and the cooling water flowing through it.

[0034] The air shut-off valve (ASV) shuts off the supply of oxidizer gas to the fuel cell (FC) through the operation control of the control unit 4.

[0035] The air pressure regulating valve (ARV) adjusts the pressure and flow rate of the oxidizer gas supplied to the fuel cell (FC).

[0036] The radiator R exchanges heat between the coolant, which has been heated by the heat generated by the fuel cell (FC), and the outside air.

[0037] Fan F increases the heat dissipation rate of radiator R.

[0038] The coolant pump WP supplies coolant cooled by the radiator R to the fuel cell FC via the intercooler IC.

[0039] The temperature detection unit St is configured, for example, with a thermistor, to detect the temperature T of the cooling water and send the detected temperature T to the control unit 4. Alternatively, the temperature detection unit St may be attached to the fuel cell FC and configured to detect the temperature T of the fuel cell FC and send the detected temperature T to the control unit 4.

[0040] Furthermore, the noise level of fan F shall be higher than that of other auxiliary equipment such as the air compressor ACP and power converter CNV. In addition, the housing of the stationary fuel cell system 1, specifically the portion of the housing near the air compressor ACP, shall be provided with holes to efficiently draw in oxidizer gas from the outside. Therefore, fan F shall be mounted at a distance from the air compressor ACP to prevent noise from fan F from leaking to the outside through these holes.

[0041] Furthermore, auxiliary equipment such as the fan F and air compressor ACP are controlled to operate so that the temperature T of the cooling water or fuel cell FC follows the target temperature Tt. For example, as the target temperature Tt increases, the rotation speed of the motors in the fan F and cooling water pump WP decreases. Therefore, by raising the target temperature Tt, the noise of the stationary fuel cell system 1 can be reduced.

[0042] The power converter CNV is connected downstream of the fuel cell FC and converts the voltage output from the fuel cell FC to a predetermined voltage. The power output from the power converter CNV is supplied to various auxiliary equipment, including the load Lo and energy storage device B, as well as the fan F, air compressor ACP, cooling water pump WP, circulation pump HP, main shut-off valve SV, air shut-off valve ASV, and air pressure regulating valve ARV.

[0043] Energy storage device B consists of lithium-ion capacitors and other components, and is connected between the power converter CNV and the load Lo.

[0044] If the difference between the power output from the power converter CNV and the total power supplied to each auxiliary device is greater than the required power from the load Lo, then the power equivalent to the required power is supplied to the load Lo, and the remaining power is supplied to the energy storage device B. When power is supplied from the power converter CNV to the energy storage device B, the energy storage device B is charged, and the charge amount C of the energy storage device B increases. Also, if the difference between the power output from the power converter CNV and the total power supplied to each auxiliary device is less than the required power from the load Lo, then the supplied power is supplied to the load Lo, and the remaining power is supplied to the load Lo from the energy storage device B. When power is supplied from the energy storage device B to the load Lo, the energy storage device B is discharged, and the charge amount C of the energy storage device B decreases. Note that the charge amount C is defined as the charge rate [%] of the energy storage device B (the ratio of the remaining capacity to the full charge capacity of the energy storage device B), or the open-circuit voltage [V] of the energy storage device B when no current is flowing through it, or the closed-circuit voltage [V] of the energy storage device B when current is flowing through it, or the integrated value [Ah] of the current flowing through the energy storage device B.

[0045] The current sensor Sif is composed of a shunt resistor, a Hall element, etc., and detects the current Ifc flowing from the fuel cell FC to the power converter CNV, and sends the detected current Ifc to the control unit 4.

[0046] The voltage sensor Svf is composed of voltage divider resistors and the like, detects the voltage Vfc of the fuel cell FC, and sends the detected voltage Vfc to the control unit 4.

[0047] The user interface (UI) is comprised of, for example, a touch panel display. When instructions are input from a user or administrator (such as the desired operating mode for the stationary fuel cell system 1 or the permissible noise level for the stationary fuel cell system 1), the UI sends the input instructions to the control unit 4. The user interface (UI) also displays information to the user (such as the current operating mode and current noise level).

[0048] Memory unit 2 consists of RAM (Random Access Memory) and ROM (Read Only Memory), and stores maps and other data, which will be described later.

[0049] Here, Figure 2 shows an example of a map stored in the memory unit.

[0050] In the two-dimensional coordinate system shown in Figure 2(a), the horizontal axis represents the control amount Cnt of the auxiliary equipment, the vertical axis represents the noise level of the stationary fuel cell system 1, and the solid line shows map M1, which illustrates the correspondence between the control amount Cnt of the auxiliary equipment and the noise level of the stationary fuel cell system 1. In map M1 shown in Figure 2(a), the noise level of the stationary fuel cell system 1 increases as the control amount Cnt of the auxiliary equipment increases.

[0051] For example, map M1 shows the relationship between the rotational speed of fan F, which has been determined in advance through experiments or simulations, and the noise level of the stationary fuel cell system 1. It is assumed that as the rotational speed of fan F increases, the noise generated from fan F increases, and the noise level of the stationary fuel cell system 1 increases.

[0052] Alternatively, map M1 shows the correspondence between the rotational speed of the motor in the air compressor ACP, which has been determined in advance through experiments or simulations, and the noise level of the stationary fuel cell system 1. It is assumed that as the rotational speed of the motor in the air compressor ACP increases, the noise generated from the air compressor ACP increases, and the noise level of the stationary fuel cell system 1 increases.

[0053] Alternatively, map M1 shows the correspondence between the output power of the power converter CNV, which has been determined in advance through experiments or simulations, and the noise level of the stationary fuel cell system 1. It is assumed that as the output power of the power converter CNV increases, the switching noise generated from the switching elements within the power converter CNV increases, and the noise level of the stationary fuel cell system 1 increases.

[0054] Alternatively, map M1 shows the correspondence between the rotational speed of the motor in the cooling water pump WP, which has been determined in advance through experiments or simulations, and the noise level of the stationary fuel cell system 1. It is assumed that as the rotational speed of the motor in the cooling water pump WP increases, the noise generated from the cooling water pump WP increases, and the noise level of the stationary fuel cell system 1 increases.

[0055] Alternatively, map M1 shows the correspondence between the rotational speed of the motor in the circulation pump HP, which has been determined in advance through experiments or simulations, and the noise level of the stationary fuel cell system 1. It is assumed that as the rotational speed of the motor in the circulation pump HP increases, the noise generated from the circulation pump HP increases, and the noise level of the stationary fuel cell system 1 increases.

[0056] Furthermore, as the power generated by the fuel cell FC increases, the rotational speed of the fan F, the rotational speed of the motor in the air compressor ACP, the output power of the power converter CNV, the rotational speed of the motor in the cooling water pump WP, and the rotational speed of the motor in the circulation pump HP will each increase, and the noise from the fan F, air compressor ACP, power converter CNV, cooling water pump WP, and circulation pump HP will each increase.

[0057] Furthermore, as the temperature T detected by the temperature detection unit St increases, the rotational speed of the fan F, the rotational speed of the motor in the air compressor ACP, the output power of the power converter CNV, the rotational speed of the motor in the cooling water pump WP, and the rotational speed of the motor in the circulation pump HP also increase, and the noise from the fan F, air compressor ACP, power converter CNV, cooling water pump WP, and circulation pump HP increases accordingly.

[0058] Furthermore, if the noise levels are as follows: fan F > air compressor ACP > power converter CNV > cooling water pump WP or circulation pump HP, then suppressing the noise of fan F and air compressor ACP in particular is effective in reducing the noise level of the stationary fuel cell system 1.

[0059] Furthermore, in the two-dimensional coordinate system shown in Figure 2(b), the horizontal axis represents the power generated by the fuel cell FC (Power Pow), the vertical axis represents the noise level of the stationary fuel cell system 1, and the solid line shows map M2, which illustrates the correspondence between the power generated by the fuel cell FC (Power Pow) and the noise level of the stationary fuel cell system 1. In map M2 shown in Figure 2(b), as the power generated (Power Pow) increases, the noise from the fan F, air compressor ACP, power converter CNV, cooling water pump WP, and circulation pump HP also increases, resulting in a higher noise level for the stationary fuel cell system 1.

[0060] Furthermore, in the two-dimensional coordinate system shown in Figure 2(c), the horizontal axis represents the temperature T detected by the temperature detection unit St, the vertical axis represents the noise level of the stationary fuel cell system 1, and the solid line represents map M3 showing the correspondence between the temperature T detected by the temperature detection unit St and the noise level of the stationary fuel cell system 1. In map M3 shown in Figure 2(c), the noise level of the stationary fuel cell system 1 increases as the temperature T increases.

[0061] The memory unit 2 is assumed to store at least one of the maps M1 to M3.

[0062] Furthermore, the communication device 3 shown in Figure 1 is a communication interface circuit that is connected to an external terminal UN via a communication network such as a LAN (Local Area Network) or WAN (Wide Area Network), and performs data conversion between the external terminal UN and the control unit 4.

[0063] The control unit 4 is composed of a microcomputer and the like.

[0064] Furthermore, the control unit 4 switches the operating mode of the fuel cell FC from normal operation mode to silent operation mode, or from silent operation mode to normal operation mode, depending on instructions from the user or administrator, or the time of day.

[0065] Furthermore, when the fuel cell stack FCS is generating power in normal operation mode or silent operation mode, the control unit 4 changes the target power generation Pt in steps according to the charge amount C of the energy storage device B.

[0066] Furthermore, the control unit 4 changes the target power generation Pt so that the temperature T detected by the temperature detection unit St follows the target temperature Tt during normal operation mode or silent operation mode. The target temperature Tt is the temperature T detected by the temperature detection unit St when the power generation Pow of the fuel cell FC follows the target power generation Pt during normal operation mode.

[0067] For example, if the target temperature Tt is raised to a target temperature Tt1 which is greater than the target temperature Tt, the control unit 4 increases the target power generation Pt to a target power generation Pt1 which is greater than the target power generation Pt, so that the temperature T detected by the temperature detection unit St follows the target temperature Tt1. Then, the control unit 4 increases the load of each auxiliary equipment (such as the rotational speed of the motor in the air compressor ACP) so that the power generation Pow of the fuel cell FC follows the target power generation Pt1.

[0068] Furthermore, if the target temperature Tt is reduced to a target temperature Tt2 which is lower than the target temperature Tt, the control unit 4 reduces the target power generation Pt to a target power generation Pt2 which is lower than the target power generation Pt1, so that the temperature T detected by the temperature detection unit St follows the target temperature Tt2. Then, the control unit 4 reduces the load of each auxiliary equipment (such as the rotational speed of the motor in the air compressor ACP) so that the power generation Pow of the fuel cell FC follows the target power generation Pt2.

[0069] Furthermore, in silent operation mode, the control unit 4 controls the operation of auxiliary equipment (target power generation Pt) so that the noise level of the stationary fuel cell system 1 is kept below the permissible value. The permissible value is an arbitrary value predetermined by, for example, the user or administrator, and is determined according to ordinances and regulations set by the national or local government, depending on the installation location and time of day of the stationary fuel cell system 1.

[0070] Furthermore, the control unit 4 receives an acceptable noise level for the stationary fuel cell system 1 from the user interface UI. This allows the noise level of the stationary fuel cell system 1 to be reduced to the noise level desired by the user.

[0071] Alternatively, the control unit 4 receives an acceptable noise level for the stationary fuel cell system 1 from an external terminal UN via the communication device 3. This allows the noise level of the stationary fuel cell system 1 to be reduced to the noise level transmitted from the external terminal UN without having to travel to the stationary fuel cell system 1, which is installed in a remote location.

[0072] <Example 1> Figure 3 is a flowchart showing the operation of the control unit 4 in silent operation mode in Example 1.

[0073] First, the control unit 4 sets an upper limit (step S101).

[0074] Next, if the control unit 4 determines that the control amount Cnt of the auxiliary equipment exceeds the upper limit set in step S101, or that the power generated by the fuel cell FC Pow exceeds the upper limit set in step S101, or that the temperature T detected by the temperature detection unit St exceeds the upper limit set in step S101 (step S102: Yes), it raises the target temperature Tt (step S103). For example, the control unit 4 raises the target temperature Tt to target temperature Tt1. By raising the target temperature Tt in this way, the rotation speed of the fan F and the motor in the cooling water pump WP can be reduced, thereby suppressing the noise of the fan F, which has a relatively high noise level among the auxiliary equipment, and reducing the noise of the stationary fuel cell system 1.

[0075] Then, if the temperature T detected by the temperature detection unit St exceeds the target temperature Tt (step S104: Yes), the control unit 4 limits the power generation Pow of the fuel cell FC (step S105). Limiting the power generation Pow of the fuel cell FC in this way suppresses the heat generation of the fuel cell FC, thereby suppressing the temperature rise of the fuel cell FC. In addition, the rotation speed of the fan F, the rotation speed of the motor in the air compressor ACP, the output power of the power converter CNV, the rotation speed of the motor in the cooling water pump WP, and the rotation speed of the motor in the circulation pump HP are reduced, so noise from the fan F, air compressor ACP, power converter CNV, cooling water pump WP, and circulation pump HP can be suppressed.

[0076] Furthermore, the control unit 4 does not raise the target temperature Tt and does not limit the power generated by the fuel cell FC if the control amount Cnt of the auxiliary equipment does not exceed the upper limit set in step S101, the power generated by the fuel cell FC Pow does not exceed the upper limit set in step S101, the temperature T detected by the temperature detection unit St does not exceed the upper limit set in step S101 (step S102: No), or the temperature T detected by the temperature detection unit St does not exceed the target temperature Tt (step S104: No).

[0077] Here, for example, let's assume that the map M1 shown in Figure 2(a) is stored in the memory unit 2, and the permissible noise level set by instructions from a user or administrator is the permissible value Nth.

[0078] In this case, when in silent operation mode, the control unit 4 refers to the map M1 shown in Figure 2(a) and sets the control quantity Cntα, which corresponds to the noise level equivalent to the allowable value Nth, as the upper limit.

[0079] Next, if the rotational speed of the fan F exceeds the controlled amount Cntα, the control unit 4 raises the target temperature Tt to the target temperature Tt1.

[0080] Then, if the temperature T detected by the temperature detection unit St exceeds the target temperature Tt1, the control unit 4 increases the target power generation power Pt to the target power generation power Pt1.

[0081] Alternatively, consider the case where the map M2 shown in Figure 2(b) is stored in the memory unit 2, and the permissible noise level set by instructions from a user or administrator is the permissible value Nth.

[0082] In this case, the control unit 4 refers to the map M2 shown in Figure 2(b) and sets the generated power Powα corresponding to the noise level equivalent to the allowable value Nth as the upper limit.

[0083] Next, the control unit 4 raises the target temperature Tt to the target temperature Tt1 if the generated power Pow, which is the product of the current Ifc and the voltage Vfc, exceeds the generated power Powα.

[0084] Then, if the temperature T detected by the temperature detection unit St exceeds the target temperature Tt1, the control unit 4 increases the target power generation power Pt to the target power generation power Pt1.

[0085] Alternatively, consider the case where the map M3 shown in Figure 2(c) is stored in the memory unit 2, and the permissible noise level set by instructions from a user or administrator is the permissible value Nth.

[0086] In this case, the control unit 4 refers to the map M3 shown in Figure 2(c) and sets the temperature Tα corresponding to the noise level equivalent to the allowable value Nth as the upper limit.

[0087] Next, if the temperature T detected by the temperature detection unit St exceeds the temperature Tα, the control unit 4 raises the target temperature Tt to the target temperature Tt1.

[0088] Then, if the temperature T detected by the temperature detection unit St exceeds the target temperature Tt1, the control unit 4 increases the target power generation power Pt to the target power generation power Pt1.

[0089] According to the stationary fuel cell system 1 in Example 1, an upper limit can be easily set relative to the permissible value by referring to a map M1 showing the correspondence between the control amount Cnt of the auxiliary equipment and the noise level of the stationary fuel cell system 1, a map M2 showing the correspondence between the power generated by the fuel cell FC and the noise level of the stationary fuel cell system 1, or a map M3 showing the correspondence between the temperature T detected by the temperature detection unit St and the noise level of the stationary fuel cell system 1. Therefore, it is not necessary to prepare multiple upper limits for various conditions such as the installation location and time of day of the stationary fuel cell system 1 and to switch between these multiple upper limits according to various conditions, and the noise of the stationary fuel cell system 1 can be reduced with a simple configuration.

[0090] Furthermore, with the stationary fuel cell system 1 in Example 1, the upper limit corresponding to the allowable value can be uniquely determined using maps M1 to M3, thus reducing the need for design changes according to user and administrator specifications, and thereby lowering manufacturing costs.

[0091] <Example 2> Figure 4 is a flowchart showing the operation of the control unit 4 in silent operation mode in Embodiment 2. Steps S101 to S105 shown in Figure 4 are the same as steps S101 to S105 shown in Figure 3, so their explanation is omitted.

[0092] After raising the target temperature Tt (step S103), the control unit 4 calculates the impedance of the fuel cell FC (step S201). If the impedance calculated in step S201 exceeds a threshold (step S202: Yes), it lowers the target temperature Tt (step S203). The threshold is a value determined in advance through experiments or simulations, and is, for example, the impedance of the fuel cell FC when the maximum voltage of the fuel cell FC begins to fall below the rated voltage due to deterioration of the fuel cell FC caused by drying inside the fuel cell FC.

[0093] For example, the control unit 4 calculates the impedance of the fuel cell (FC) using well-known impedance calculation methods such as the electrochemical impedance method or the AC impedance method.

[0094] Furthermore, if the impedance calculated in step S201 exceeds a threshold, the control unit 4 lowers the target temperature Tt to target temperature Tt2. The target temperature Tt2 may be a value determined in advance through experiments or simulations, or it may be a value determined by the difference between the threshold and the impedance calculated in step S201.

[0095] Generally, the lower the moisture content inside a fuel cell (FC), that is, the drier the FC becomes, the higher its impedance. Therefore, if the impedance of a fuel cell is relatively high, it can be inferred that the FC is dry.

[0096] Furthermore, when the target temperature Tt is increased, if the power demanded from the load Lo is relatively large, the target supply amount of oxidizer gas from the air compressor ACP to the fuel cell FC increases, making the inside of the fuel cell FC more prone to drying.

[0097] Therefore, in the control unit 4 of Example 2, if the impedance of the fuel cell FC exceeds a threshold, the target temperature Tt is lowered. As a result, the target power generation Pt of the fuel cell FC decreases, which reduces the rotational speed of the motor in the air compressor ACP, decreases the amount of oxidant gas supplied from the air compressor ACP to the fuel cell FC, mitigates drying inside the fuel cell FC, and suppresses the voltage drop of the fuel cell FC due to deterioration of the fuel cell FC. In addition, by lowering the target temperature Tt, the target power generation Pt of the fuel cell FC decreases, so not only the air compressor ACP but also other auxiliary equipment are subjected to a lower load, and thus the noise of the stationary fuel cell system 1 can be reduced.

[0098] <Example 3> Figure 5 is a flowchart showing the operation of the control unit 4 in silent operation mode in Embodiment 3. Steps S101 to S105 and S203 shown in Figure 5 are the same as steps S101 to S105 and S203 shown in Figure 4, so their explanation is omitted.

[0099] After raising the target temperature Tt (step S103), if the rotational speed of the motor in the air compressor ACP exceeds the upper limit (step S301: Yes), the control unit 4 lowers the target temperature Tt (step S203) and determines whether the temperature T detected by the temperature detection unit St exceeds the target temperature Tt lowered in step S203 (step S104). For example, if the rotational speed of the motor in the air compressor ACP exceeds the upper limit, the control unit 4 lowers the target temperature Tt to target temperature Tt2. The control unit 4 refers to the map M1 shown in Figure 2(a) and sets the control amount Cntα (rotational speed of the motor in the air compressor ACP) corresponding to the noise level equivalent to the allowable value Nth as the upper limit.

[0100] Furthermore, if the rotational speed of the motor in the air compressor ACP does not exceed the upper limit (step S301: No), the control unit 4 does not lower the target temperature Tt and determines whether the temperature T detected by the temperature detection unit St exceeds the target temperature Tt that was raised in step S201 (step S104).

[0101] When the target temperature Tt is increased, if the power demanded from the load Lo is relatively large, the target supply amount of oxidizer gas from the air compressor ACP to the fuel cell FC increases. This raises concerns that the rotational speed of the motor inside the air compressor ACP will increase, leading to increased noise from the air compressor ACP.

[0102] Therefore, in the control unit 4 of Example 3, after raising the target temperature Tt, if the rotational speed of the motor in the air compressor ACP exceeds the upper limit, the target temperature Tt is lowered. This reduces the rotational speed of the motor in the air compressor ACP, thereby suppressing the noise of the air compressor ACP and reducing the noise of the stationary fuel cell system 1.

[0103] It should be noted that the present invention is not limited to the embodiments described above, and various improvements and modifications are possible without departing from the spirit of the invention. [Explanation of Symbols]

[0104] 1. Fuel cell system 2 Storage section 3. Communication device 4. Control Unit Lo load FC fuel cell HT fuel tank SV Main stop valve INJ Injector GLS gas-liquid separator HP Circulation Pump EDV Exhaust Drain Valve DIL Diluent ACP Air Compressor ARV Air Pressure Regulating Valve ASV Air Shut-Off Valve R Radiator F Fan WP Water Pump IC Intercooler CNV Power Converter B Energy storage device Sif current sensor SVF voltage sensor UN External Terminal

Claims

1. A stationary fuel cell system equipped with a fuel cell, A temperature detection unit for detecting the temperature of the cooling water used to cool the fuel cell or the temperature of the fuel cell, Auxiliary equipment for generating electricity from the aforementioned fuel cell, A control unit controls the operation of the auxiliary equipment so that the temperature detected by the temperature detection unit follows the target temperature, Equipped with, The control unit has a map showing the correspondence between the control amount of the auxiliary equipment and the noise level of the stationary fuel cell system. When attempting to keep the noise level of the stationary fuel cell system below an acceptable value, the control unit refers to the map and sets the control amount corresponding to the noise level equivalent to the acceptable value as an upper limit. If the control amount of the auxiliary equipment exceeds the upper limit, the control unit raises the target temperature. A stationary fuel cell system characterized by the following features.

2. A stationary fuel cell system comprising a fuel cell, A temperature detection unit for detecting the temperature of the cooling water used to cool the fuel cell or the temperature of the fuel cell, Auxiliary equipment for generating electricity from the aforementioned fuel cell, A control unit controls the operation of the auxiliary equipment so that the temperature detected by the temperature detection unit follows the target temperature, Equipped with, The control unit has a map showing the correspondence between the power generated by the fuel cell and the noise level of the stationary fuel cell system. When attempting to keep the noise level of the stationary fuel cell system below an acceptable level, the control unit refers to the map and sets the power generated corresponding to the noise level equivalent to the acceptable level as an upper limit. If the power generated by the fuel cell exceeds the upper limit, the control unit raises the target temperature. A stationary fuel cell system characterized by the following features.

3. A stationary fuel cell system comprising a fuel cell, A temperature detection unit for detecting the temperature of the cooling water used to cool the fuel cell or the temperature of the fuel cell, Auxiliary equipment for generating electricity from the aforementioned fuel cell, A control unit controls the operation of the auxiliary equipment so that the temperature detected by the temperature detection unit follows the target temperature, Equipped with, The control unit has a map showing the correspondence between the temperature detected by the temperature detection unit and the noise level of the stationary fuel cell system. When attempting to keep the noise level of the stationary fuel cell system below an acceptable value, the control unit refers to the map and sets the temperature corresponding to the noise level equivalent to the acceptable value as an upper limit. If the temperature detected by the temperature detection unit exceeds the upper limit, the control unit raises the target temperature. A stationary fuel cell system characterized by the following features.

4. A stationary fuel cell system according to any one of claims 1 to 3, The control unit changes the tolerance value based on user instructions. A stationary fuel cell system characterized by the following features.

5. A stationary fuel cell system according to claim 4, The control unit modifies the tolerance value based on instructions transmitted from an external terminal located outside the stationary fuel cell system. A stationary fuel cell system characterized by the following features.

6. A stationary fuel cell system according to any one of claims 1 to 3, If, after raising the target temperature, the control unit detects that the temperature detected by the temperature detection unit exceeds the target temperature after the rise, it limits the power generation of the fuel cell. A stationary fuel cell system characterized by the following features.

7. A stationary fuel cell system according to any one of claims 1 to 3, After raising the target temperature, the control unit lowers the target temperature if the impedance of the fuel cell exceeds a threshold. A stationary fuel cell system characterized by the following features.

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